Well yes I have. All photos of all of my horses are on my website and all of my mares are inspected/approved (with the exception of the youngsters obviously). Including a mare that I had to petition the board for betterment of the breed.
feel free to call or email me and I'd be happy to chat with you about inspections etc.
As for any harder or not - the short answer is yes and no. The T'bred mare has to score higher than a TK mare (the theory is they are supposed to be improving the breed so they better be better) and the inspectors do take a harder look at them (and Arab mares), BUT a good mare is a good mare.
I had a great time at the only TK inspection I went through with my Thoroughbred mare. I will have to brag about her a bit. Although 14 years of age, pregnant and not in shape, she scored a 52, which is pretty unheard of for a Thoroughbred and would be a high score for a TK. The only mare that scored higher was a purebred TK mare, 1/2 her age and in show shape. The president of the Assoc conducted the inspection, was very approachable, explained everything and it was inviting and enjoyable. A great learning experience and very positive. I think the ATA is very receptive to Thoroughbred mares of quality. That said, the other TB mare presented scored in the 40's and was not accepted, so be sure you present a mare that is worth breeding.